LED Vs. Transistor Vs. ? Clipping

[warwick.hoy]

Help me to understand...

Okay so there is LED clipping and transistor clipping, Tube clipping obviously, but what else?

What are the differences sound wise?

What is more desirable?

I didn't do a search, but it isn't something I see discussed very often.

[dannybuoy]

You forgot diode clipping, which is the most common (muffs, tubescreamers, etc)! LED is a light-emitting-diode, some pedals (I think a TurboRAT for instance) use LED clipping. As for the sound differences, I don't really know!

[warwick.hoy]

I bring it up because I discovered that the SD-2 is LED clipping.

By Diode,...is that referring to Germanium,...Silicon or is that transistor?

[dannybuoy]

Diodes can be made of silicon or germanium, they are semiconductors as are transistors:

http://en.wikipedia.org/wiki/Diode

These little silicon 1N4148 ones are quite common in muff clones etc:



I started getting into building my own pedals, learned a lot about circuits, bought a few parts etc... then realised I'd rather spend my time playing bass than playing with a soldering iron! If I won the lottery and didn't have a day job, I'd have time for hobbies like this but right now I don't have the time to get into building my own pedals. One day I shall build my Nocto Loco kit that's been sitting here for months!

[B.C.]

Originally Posted by warwick.hoy

I bring it up because I discovered that the SD-2 is LED clipping.

By Diode,...is that referring to Germanium,...Silicon or is that transistor?

Clipping is usually done these days via Silicon Diodes. Led clipping is a specialized form of this that some claim provides a softer clipping sound. THere is also Germanium Diodes, which clip much softer(I personally am not a fan, after modding a few TS for Germanium clipping.)

For Transistors, there is also Silicon and Germanium clipping. Again, Germanium is not as "harsh" as Silicon, but again, I still like Silicon. For Germanium transistor clipping, think old fuzz faces, Z.vex fuzz factory,etc. For Silicon, check out the more modern transistor circuits, such as the newer Z.vex designs like the Box of Rocks, etc.

I tried to avoid EE jargon, but would be happy to explain if you wish.

[warwick.hoy]

As a future EE major, any insight into the jargon is much appreciated.

So a diode is a transistor (same thing different terms)?

Can you clip an opamp?

EDIT: For clarification; clipping is what gives you the OD/distortion/Fuzz sound....yes?

[B.C.]

Originally Posted by warwick.hoy

As a future EE major, any insight into the jargon is much appreciated.

So a diode is a transistor (same thing different terms)?

Can you clip an opamp?

EDIT: For clarification; clipping is what gives you the OD/distortion/Fuzz sound....yes?

No, they share similarities in that they are both semi conductor devices, but thats about it.

A Diode is a device that allows a current to only pass in one direction. Clipping(yes, overdrive, distortion, etc.) is done with diodes usually by placing the diodes in anti-parallel position(in parrallel, but opposite directions). Depeding on how this is implemented in the circuit determines the softness or hardness of clipping.

A transistor is also a semiconductor device, but it is a 3(or 4) terminal device that allows a small current to control a larger current. How this is done doesn't matter for us, but a transistor has 3 basic states: Off, On, and Saturated. When the transistor is in its on state, it acts as a voltage amplifier. When in Saturated, it can be thought of as a switch(how digital 1's and 0's are made.)

Op Amps can be used as gain devices, but this is usually done in compliment with the diode clipping. The Tubescreamer works in this way.

[seamonkey]

A diode if put across an input will do soft clipping.
Silicon diode will gently break over at around .7 V
Germanium around .3v
LED's vary but around 2-4 V typically

If you want to passively try soft clipping, You can buy germanium diodes to wire up and replace the cap in your bass tone control. A pickup will easily drive .3v and allow the diode to clip. It's as simple as that. Potted in plastic they cost $27, but you can buy the diodes yourself for pennies.
http://www.stewmac.com/shop/Electron...overdrive.html

Add circuits around diodes you can get hard clipping. Early and still popular transistor fuzz boxes skip the diodes but are essentially small amplifiers designed to hard clip. They usually add a cap for a tone control to filter out extra highs. Which takes it back down to soft clipping.

[warwick.hoy]

Thanks for sharing guys. I'm not building pedals yet, but I find this stuff very interesting, and it helps me understand my effects more than you know.

[OxJohnson]

Germanium diodes are typically considered better than silicon for sound just as tubes are commonly preferred over transistors. Truth be told both tubes and germanium are actually "crappier" than their silicon counterparts. This is because "leak" current, which is why they clip softer.

AFAIK, germanium diodes (and transistors) are not made anymore. They were the precursor to silicon in solid state components. I actually still have some germanium diodes AND transistors. I have been offered A LOT of money for the transistors.

Ox.

[bongomania]

A common mod for dirt pedals is to replace silicon diodes with LEDs. Depending on the pedal this may also necessitate replacing nearby resistors for proper voltage levels. The LEDs can be "tubier" sounding and smoother (depending on the circuit).

[chicago_mike]

You could always devise a circuit to switch between different forms of clipping.

[whoatherechunk]

I tend to prefer nail clipping since I don't do it often.

[mikeboth]

Originally Posted by OxJohnson

AFAIK, germanium diodes (and transistors) are not made anymore.

Both devices are still available new from a number of sources. Whether or not they are useful in a particular FX circuit is a separate issue.

I have been offered A LOT of money for the transistors.

... which are worth practically nothing if their leakage is too high.

[bongomania]

Yeah, I've bought literally hundreds of germ xtrs from vintage surplus suppliers, and every single one of them was garbage. Used to be you could cherry-pick one good one out of any pile of ten or so, but not so much anymore. That's just in re: the old ones, though, I haven't tried any of the new ones.

[OxJohnson]

Originally Posted by mikeboth

Both devices are still available new from a number of sources. Whether or not they are useful in a particular FX circuit is a separate issue.



... which are worth practically nothing if their leakage is too high.

That is true! I put them on my handy dandy HFE tester and got enough for 5 matched pairs... I agree with Bongo though, if you don't have a DMM in hand then either (1) pass or (2) buy A LOT!

As far as "new" goes... who still manufactures them?! I know that you can still get NOS, but I didn't think that you can get them newly manufactured...

Ox.

EDIT: I have one set that matches at an HFE of 110, which is almost perfect for an overdrive that I was looking to build awhile back.

[BassJunkie730]

I just want to clarify what has been said about replacing si diodes wth led.

LEDs are LESS compressed sounding than si diodes
and offer a higher volume level, which depending on the circuit could lend a stiffer or a more "at the edge of a cliff" sound
LEDs can sound tubey because that tend to increase the dynic response of the clipping. Which may or may not be your thing.

The track in my sig has a baseline that uses a modified ds-1 that has doubled up anti parallel. One side is a series pair of LEDs and the other a series pair of si diodes.

You should really build a simple boost pedal an experiment with all the different combos and single clipping component types to get a hands
on grasp of what they do. A great project for you student EE guys

[B.C.]

Originally Posted by BassJunkie730

I just want to clarify what has been said about replacing si diodes wth led.

LEDs are LESS compressed sounding than si diodes
and offer a higher volume level, which depending on the circuit could lend a stiffer or a more "at the edge of a cliff" sound
LEDs can sound tubey because that tend to increase the dynic response of the clipping. Which may or may not be your thing.

The track in my sig has a baseline that uses a modified ds-1 that has doubled up anti parallel. One side is a series pair of LEDs and the other a series pair of si diodes.

You should really build a simple boost pedal an experiment with all the different combos and single clipping component types to get a hands
on grasp of what they do. A great project for you student EE guys

IMHO, I agree with most of this. The LED is less compressed, but IME clips a little softer than a normal silicon diode.

As per Bongo's comment, I agree, both are made but man, finding good ones is really difficult.

Yeah, I really easy circuit to build is the LPB-1 circuit. Simple and still introduces one to transistors. I like to use a Fet in place of the BJT.

[jimmy rocket]

Originally Posted by chicago_mike

You could always devise a circuit to switch between different forms of clipping.

That's what that little switch on the right does. Up for Asymmetrical Silicon diode clipping, down for LED clipping.



The LED's do sound a bit more tube like in this circuit (a modded 808 clone), but the asymmetrical diodes sound pretty gnarly themselves.

[warwick.hoy]

Originally Posted by mikeboth

Both devices are still available new from a number of sources. Whether or not they are useful in a particular FX circuit is a separate issue.



... which are worth practically nothing if their leakage is too high.

As in they leak themselves, or there is some sort of audio issue?